function dl=dldr(alpha,beta)
a=[.005 .017 .014 .010 -.005 .009 .019 .005 -.000 -.005 -.011 .008
.007 .016 .014 .014 .013 .009 .012 .005 .000 .004 .009 .007
.013 .013 .011 .012 .011 .009 .008 .005 -.002 .005 .003 .005
.018 .015 .015 .014 .014 .014 .014 .015 .013 .011 .006 .001
.015 .014 .013 .013 .012 .011 .011 .010 .008 .008 .007 .003
.021 .011 .010 .011 .010 .009 .008 .010 .006 .005 .000 .001
.023 .010 .011 .011 .011 .010 .008 .010 .006 .014 .020 .000]';
s=.2*alpha;
k=fix(s);
if(k<=-2),k=-1;end
if(k>=9),k=8;end
da=s-k;
l=k+fix(1.1*sign(da));
s=.1*beta;
m=fix(s);
if(m<=-3),m=-2;end
if(m>=3),m=2;end
db=s-m;
n=m+fix(1.1*sign(db));
l=l+3;
k=k+3;
m=m+4;
n=n+4;
t=a(k,m);
u=a(k,n);
v=t+abs(da)*(a(l,m)-t);
w=u+abs(da)*(a(l,n)-u);
dl=v+(w-v)*abs(db);
